Ion mobility spectrometry (IMS) refers to an analytical technique that can be used to separate and identify ionized material, such as molecules and atoms. Ionized material can be identified in the gas phase based on mobility in a carrier buffer gas. Thus, an ion mobility spectrometer (IMS) can identify material from a sample of interest by ionizing the material and measuring the time it takes the resulting ions to reach a detector. An ion's time of flight is associated with its ion mobility, which relates to the mass and geometry of the material that was ionized. The output of an IMS detector can be visually represented as a spectrum of peak height versus drift time.
IMS detectors and other detectors often include a vapour generator to supply a dopant chemical to the detector. Vapour generators can also be used to supply a test chemical for use in testing or calibrating a detector, a filter or other equipment. In some applications it is important that the vapour generator can be switched on and off rapidly, and that leakage can be prevented when the detector is switched off. For example, in an IMS detection system, rapid switching of the vapour generator on and off enables rapid switching between different doping conditions, such as different levels of dopant or different dopant substances. Such rapid switching could also enable different regions of the IMS detector to be doped differently by ensuring there was no leakage to undoped regions of the apparatus when the apparatus is switched off.